The principal goal of this investigation is to determine the mechanism of induction of the set of liver enzymes that catalyze the synthesis of long chain fatty acids. The present use of maintenance cultures of mature hepatocytes will be emphasized initially to achieve evidence that insulin is the primary external signal for initiating the net synthesis of the lipogenic enzyme set. The rate of synthesis of key lipogenic enzymes will be measured in vitro by pulse labeling with amino acids. A study will be made to ascertain whether the primary insulin induction process requires the support of other hormones. Once the induction process is well characterized in cultured hepatocytes a delineation of preinduction events will be undertaken. These include: change in concentration and flux of key lipogenic precursors as a function of time following the insulin signal; change in concentration of the inactive (phosphorylated) and active (dephosphorylated) forms of pyruvate kinase, acetyl CoA carboxylase and the fatty acid synthetase complex as a function of preinduction time; and change in concentration of total and specific mRNA harvested from hepatocyte polysomes. Provided these studies show that hepatocytes cultured in vitro retain the principal features of events associated with the induction process in vivo an examination will be made of the pattern of phosphorylation of non histone proteins of liver nuclear chromatin. BIBLIOGRAPHIC REFERENCES: Geelen, M. J. H., Pruden, E. L. and Gibson, D. M.; Restoration of Glycogenesis in Hepatocytes from Starved Rats, Life Science, in press (February 1977). Geelen, M. J. H., Vaartjes, W. J. and Gibson, D. M.; Levels of 3'-5'-Cyclic Adenosine Monophosphate (cAMP) in Maintenance Cultures of Rat Hepatocytes in Response to Insulin and Glucagon, Lipids, in press (March 1977).